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I have a shapefile that I have loaded as a GeoPandas GeoDataFrame, and it has a geometry column containing polygons and multipolygons.

My end goal is to do some zonal computations on a GeoTiff raster, in particular, I want to compute the mean value within each polygon, and also count the number of pixels that contributed to that polygon's zonal mean. Here's a link to another GIS-SE question of mine that outlines my attempts to do that so far using GDAL and rasterstats.

I am just wondering if GeoPandas is up to zonal calculations yet. If I open a raster in GDAL/numpy/rasterio and load the shapefile in a GeoPandas GeoDataFrame, is there a way to compute the number of raster pixels inside each polygon?

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  • Could you clarify what you mean by 'count the number of pixels'?
    – juturna
    May 29, 2015 at 13:43
  • My apologies, I'm new to GIS and wasn't thinking straight. Obviously the shapefile doesn't have pixels, I was thinking of the GeoTiff raster I want to overlay. I'll delete this question May 29, 2015 at 14:16
  • So you are looking for the number of pixels in the raster within each polygon? You can edit your question to clarify what you are asking.
    – juturna
    May 29, 2015 at 14:23

2 Answers 2

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You can do zonal statistics from a GeoDataFrame directly on a GeoTiff using rasterstats.

import geopandas as gpd
from rasterstats import zonal_stats

geodf = gpd.read_file("foo.shp")
zonal_stats(geodf, "bar.tif")

There are some good examples of rasterstats integration on the wiki.

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  • Yes - I did go with rasterstats in the end and it works great. Oct 26, 2015 at 18:29
  • do these stats reflect the values of the pixels? or their area?
    – fccoelho
    Dec 3, 2016 at 17:35
  • @fccoelho Zonal statistics are descriptive statistics (mean, median, min, max, etc) of the set of pixels which intersect a geometry. Thus both the number of pixels (roughly equivalent to the area of the geometry) and the value of those pixels are considered.
    – perrygeo
    Dec 4, 2016 at 23:33
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By "count the number of pixels" do mean the area of each polygon? If so,

mygeodf.area
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  • 2
    Thanks for your answer. My question didn't make any sense, so I've updated it. May 29, 2015 at 14:56

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